Researchers Question Paleo Diet's Carb Restrictions

Next time, have some potatoes with that steak—the original Paleo dieters likely did. Mitch Mandel

The Paleo diet has taken off in recent years, buoyed by the thinking that eating like our ancestors might reverse climbing rates of obesity, diabetes, and cardiovascular disease. The diet emphasizes meat, vegetables, fruit, and nuts, and eliminates dairy and grains. But a recent article in The Quarterly Review of Biology claims that it might be missing one of the biggest components of the prehistoric diet: starchy carbohydrates.

The researchers compiled evidence from genetics, archaeology, physiology, and nutrition to create a theory that our Paleolithic ancestors (living between 2.5 million and 10,000 years ago) did eat starchy plants like potatoes, possibly even cooking them over fires. They argue that the addition of carbs helped promote the growth of our large brains.

Karen Hardy, Ph.D., from the Autonomous University of Barcelona in Spain and an author of the new review, said that, without carbs, we wouldn’t be the people we are today. “I don’t think we’d be here if we actually followed what the proponents of the Paleo diet suggest,” said Hardy.

We also might not be runners. Carbohydrates are essential for long-distance running, which is how our ancestors chased down and captured prey, said Hardy. During vigorous exercise, our bodies get energy from using glycogen stored in our muscles. After about twenty miles, we run out of glycogen stores, and—if we haven’t been restocking them with carbohydrates from sports drinks, gels, or food—we hit the wall.

Daniel Lieberman, Ph.D., author of The Story of the Human Body and an evolutionary biologist known for his work on barefoot running, agrees that the Paleo diet might be missing the mark. “The idea that people shouldn’t eat carbohydrates is just silly,” he said. “We’ve been eating a lot of carbohydrates for a long time.” But Lieberman isn’t sure the carbohydrates Paleolithic hunters ate actually helped their running. His research found that hunters who chased their prey didn’t run that fast; they often did a combination of running and walking. (“They would not qualify for Boston,” he said.) At those speeds, they might not have needed huge supplies of carbohydrates—their bodies might have relied on fat instead.

Some runners today think relying on fat might help their performance. The idea is that adopting a low-carbohydrate, high-fat diet (like the Paleo diet) forces our bodies to use fat—which we have plenty of—as fuel, allowing us to go farther without bonking. But there isn’t enough research on this approach and whether it’s beneficial isn’t known, Lieberman said. Some have proposed it might be better for ultra-length races. But, as speed increases, carbohydrates become vital. “If you want to run fast—long and fast—lots of carbohydrates are extremely important,” Lieberman said.

Lieberman and Hardy emphasize that the carbohydrates our ancestors ate were complex carbs, not the overly processed, refined carbohydrates on the supermarket shelves today. But Hardy thinks people should be careful when trying to replicate ancestral diets, because we don’t yet know exactly what they ate. Lieberman is wary of the diets, too. Just because our ancestors ate a certain way doesn’t mean it’s healthy. “We didn’t evolve to be healthy; we evolved to have as many offspring as we can,” he said.

But if you do decide to try to eat like our ancestors—and especially if you want to run long and fast—it looks like you can put carbs back on the table.

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